<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>盒子</title>
    <style>
        * {
            margin: 0;
            padding: 0;
        }

        .content {
            width: 1240px;
            height: 628px;
            /*background-color: yellow;*/
            border: 1px solid;
            margin: 50px auto;
        }

        .content_demo {
            width: 234px;
            height: 607px;
            border: 1px solid;
            margin-left: 8px;
            margin-top: 9px;
            display: inline-block;
            position: relative;
        }

        .content .demo {
            width: 980px;
            height: 610px;
            /*border: 1px solid;*/
            float: right;
            margin-top: 6px;
            margin-right: 8px;
            display: flex;
            /*background-color: rgba(123, 123, 123, 0.6);*/
            flex-direction: row;
            flex-flow: wrap;
            justify-content: space-between;
            align-items: stretch;

        }
        .demo_item{
            width: 235px;
            height: 300px;
            border: 1px solid;
            display: inline-block;
            margin-left: 6px;
            margin-top: 4px;
        }
    </style>
</head>
<body>
<div class="content">
    <div class="content_demo"></div>
    <div class="demo">
        <div class="demo_item">1</div>
        <div class="demo_item">2</div>
        <div class="demo_item">3</div>
        <div class="demo_item">4</div>
        <div class="demo_item">5</div>
        <div class="demo_item">6</div>
        <div class="demo_item">7</div>
        <div class="demo_item">8</div>
    </div>
</div>
</body>
</html>